1. Field of the Invention
The present invention relates to a lead frame, a semiconductor device using the same, and a method of producing the semiconductor device.
2. Description of the Background Art
There is an increasing demand for the miniaturization of semiconductor devices that implements dense mounting of semiconductor devices to a circuit board. To reduce the size of a semiconductor device, a QFN (Quad Flat Non-leaded Package), a SON (Small Outline Non-leaded Packages) and other so-called non-leaded packages are often used. While a non-leaded package, like a conventional semiconductor device, uses a lead frame, it causes the lead frame to protrude from the bottom of a semiconductor package for thereby reducing the mounting area.
The non-leaded package that makes outside electrodes not visible from above a circuit board is desirable. However, when the lead frame is required to protrude from the side of a semiconductor package, the degree of projection should be reduced as far as possible.
It is a common practice with a semiconductor device using a non-leaded package to protect external electrodes with a resin sheet during production. More specifically, the resin sheet prevents resin from leaking at the time when the resin seals a lead frame loaded with a semiconductor chip and undergone wire bonding, thereby insuring plating to follow. Therefore, the resin sheet is not a structural element of a semiconductor device or product. Because the resin sheet is expensive, it increases the production cost of the semiconductor device and thereby makes the demand for cost reduction more keen.
Moreover, in a conventional semiconductor device, part of a lead frame constituting electrode portions appear on the side of a package. It follows that when semiconductor devices are mounted to a circuit board side by side, it is necessary to guarantee a space broad enough to avoid short-circuiting ascribable to, e.g., soldering between nearby semiconductor devices. This obstructs dense mounting of semiconductor devices to a circuit board.